1Designed and built to challenge an aggressive French shipbuilding program in the late 1850s, when commissioned, the 40-gun, steam-powered, ironclad HMS Warrior was the largest warship in the world.

The revolutionary design housed the main guns, 10 boilers, and steam engine inside an impregnable armored "box", or citadel, made from 41/2in thick wrought iron plates. Warrior is the only surviving example of Britain's "Black Battlefleet"--the 45 iron hulls built for the Royal Navy between 1861 and 1877. She was restored in the 1980s and is now on public display at Portsmouth Historic Dockyard.